1. Field of the Invention
The present invention relates to an on-vehicle display device in which a display cell is prevented from being directly affected by distortion of a fixed panel to reduce display unevenness in an image displayed by the display cell.
2. Description of the Related Art
An on-vehicle display device has a fixed panel incorporated in a dashboard, an instrument panel, or the like inside a passenger cabin, and a display unit including a display cell and a backlight unit is mounted to the fixed panel. Such a type of on-vehicle display device has a problem that display unevenness occurs due to generation of distortion in the display cell when a large fixing force acts on the display cell. In recent years, an IPS liquid crystal cell has been used to secure a wide viewing angle. However, when bending stress or torsional stress acts on the liquid crystal cell, black unevenness (brightness unevenness) is likely to occur as the display unevenness.
JP 2016-122151 A describes an on-vehicle display device in which fixing stress acting on a display cell is relaxed as a countermeasure for suppressing occurrence of display unevenness. FIG. 4 illustrates an on-vehicle display device having the same structure as that described in JP 2016-122151 A as a conventional example.
In an on-vehicle display device 100 of the conventional example illustrated in FIG. 4, a Z1 direction is a front side in the display direction, and a Z2 direction is the rear. The on-vehicle display device 100 has a fixed panel 110 fixed to a vehicle body, and the display unit 101 is installed inside a frame opening 110a of the fixed panel 110.
In the display unit 101, a display cell 102 and a backlight unit 103 are supported on a cell support member 104. A display cover plate 105 is installed in a front portion of the display cell 102 in a display direction (Z1 direction). In the on-vehicle display device 100 illustrated in FIG. 4, a bracket 111 made of a metal plate is fixed to the fixed panel 110, and the cell support member 104 of the display unit 101 is fixed to the bracket 111 via a fixing mechanism 115.
In the fixing mechanism 115 described in JP 2016-122151 A, an inner diameter of a mounting hole 115b is formed to be sufficiently larger than a diameter of a shaft portion of a fixing screw 115a such that the bracket 111 and the cell support member 104 can be fixed with freedom in the front-rear direction (Z direction) in the fixing mechanism 115. Further, a back surface of the display cover plate 105 is first fixed to a front surface of the fixed panel 110 via an adhesive layer 116 in a process of assembling the on-vehicle display device 100. Thereafter, the fixing screw 115a is tightened to the fixing mechanism 115 to fix the bracket 111 and the cell support member 104.
With this assembling method, it is possible to suppress a large fixing stress from acting on the cell support member 104 by a tightening force of the fixing screw 115a of the fixing mechanism 115.
Although the fixed panel 110 is formed using a synthetic resin material or the like in the on-vehicle display device 100 illustrated in FIG. 4, due to a dimensional tolerance between the fixed panel 110 and the vehicle body, distortion is easily applied to the fixed panel 110 when the fixed panel 110 is fixed to the vehicle body.
In the on-vehicle display device 100 described in JP 2016-122151 A, an overhang 105a overhanging laterally from the display cell 102 is provided on the display cover plate 105, and a back portion of the overhang 105a is attached and fixed to the fixed panel 110. Thus, when the distortion occurs at the time of fixing to the fixed panel 110, the distortion directly acts on the display cell 102 from the display cover plate 105 so that display unevenness is likely to occur on the display cell 102.
However, when the overhang 105a of the display cover plate 105 is not supported from the back portion but left in a free state, it is difficult to secure the fixing strength of the display cover plate 105. As a result, for example, when a sensor provided at a front portion of the display unit 101 is operated by pushing with a finger or the like, the display cover plate 105 is easily deformed, and the display unevenness is likely to occur as unnecessary stress acts on the display cell 102 due to such deformation.